HVAC Belt Tension

A common belt myth is that you need to tension a belt so that it has an inch of deflection. Many factors can affect deflection, including the pressure you apply to the belt, the belt’s length, and what the belt is made of.

There are no hard, fast rules of thumb for working with belts. However, we recommend using the Browning app to help you if you’re unfamiliar with belts and typical procedures with them.

If you’re working with an adjustable drive pulley (sheave), DO NOT adjust the pulley itself to set the belt tension. Instead, you have to adjust the foot mount on the motor to set the belt tension. Before you replace the belt, check the pulley condition; the problem could lie there, not with the belt. Replace the pulley if it is damaged.

When you adjust the two halves of the pulley closer together, you can expect more airflow. When you adjust them to sit further apart, you decrease the airflow. So, you must measure airflow to set those halves correctly. We don’t typically adjust those in the field, but we have to adjust the motor base inward if we want to replace a belt.

When the old belt comes off, we want it to be loose. Of course, we must also put the new belt on loosely and tension it appropriately once we finish the replacement. You’ll want to avoid overtightening the belt, so a tensioning tool will be especially effective here.

A proper tensioning tool allows you to apply a set amount of force and then look at a fixed amount of deflection. Browning makes a tool specifically designed for this purpose.

You should not set your belt tension based on blower amperage; the blower motor could run well below its peak conditions. Instead, you want the belt to be as tight as possible without slipping or squealing under peak-load conditions. Overall, if you need to do significant adjustments, you may as well replace the belt. Always inspect the whole system if there is slippage, too.

Browning belt tensioning instructions.

Browning video on How to Check if your V-Belt is Properly Tensioned.

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